Much effort has been directed toward the development of a simple, lightweight roll control system in order to avoid the impact point errors associated with roll resonance and zero roll of an ablating ballistic reentry vehicle.
One such system is described in the patent to Durran et al U.S. Pat. No. 3,690,596 wherein variable cant angle fins are employed and wherein the cant angles of the fins are regulated by centrifugal forces accompanying an increase in roll rate.
Other systems have canted fixed fins or grooves to spin-up the vehicle to some prescribed roll rate above critical.
All of these systems require fins or grooves external to the missile to provide roll control.